Strapped magnetron and method of strapping



y 21, 1953 A. 'r. NORDSIECK 2,645,843

'STRAPPED MAGNETRON AND METHOD OF STRAPPING Filed April 9, 1946 2 Sheets-Sheet 1 INVEN TOR. ARNOLD T. NORDSIECK V W 9. Ar

' ATTORNEY July 21, 1953 v A. 'r. NORDSIECK 2,645,843

STRAPPED MAGNETRON AND METHOD OF STRAPPING Filed April 9, 1946 2 Sheets-Sheet 2 &

N-. 301W M0 IT. 2 u.

0193 'INVENTOR.

ARNOLD TNORDSIECK D, -A uf ATTORNEY Patented July 21, 1953 STRAPPED MAGNETRON AND .METHOD OF STRAPPIN G Arnold '1'. NordsieclnNew York, N.- Y., assignor to the United States of Americaas represented by the Secretary of War Application April 9, 1946, Serial No. 660,605

This invention relates to a strapped magnetro anode and a method for strapping.

One of the objects of this invention is to provide an arrangement whereby magnetron anodes may be strapped without the necessity of any machine operations on the anode other than 'hobbing and turning.

Another object of this invention is to provide jig means for attaching straps to magnetron anodes.

Still another object is to provide a method of strapping which may be applied to any magnetron anode structure in which strapping is desirable.

These and other objects will become apparent in the specification and in the attached drawings in which:

Figure 1 is a plan view of a magnetron anode with the ends unstrapped;

Figure 2 is an elevational sectional view of the anode of Figure 1;

Figure 3 shows two straps in their first stage of fabrication;

Figure 4 shows a strap in completed condition;

Figure 5 shows the, jig, straps and anode in cross section;

Figure 6 is an isometric cross sectional view of the anode strapped in accordance with the invention;

Figure 7 is an enlarged sectional view of part of the anode shown inFigure 6.

Because, of inherent characteristics of multicavity magnetron anodes such a tube is capable of oscillating in a number of modes. If the mode separation is not good one mode of oscillation will be followed by another, with the result that the output and frequency vary con-.

siderably and the tube efiiciency falls.

One method of obtaining efiiciency and good mode separation utilizes conductors attached to the ends of the anode vanes. This technique is known in the art as strapping. The method may use one circular conductor at each end of the anode connecting alternate vanes that is single ring strapping, or two circular conductors at each end of the anode also connecting alternate vanes or double ring strapping. The latter is preferable in man instances because of the better mode separation it alfords, and has been widely used with successful results, particularly in anodes of reasonably large physical size.

However, with the demands for increased frequency the resultant anodes have become smaller and have a large number of cavities, and the 2 Claims. (0]. 29-2514) tory in performance have been objectionable be cause of the great expense involved in view of the skilled labor'required'and the delicacy of the parts and the unavoidably small tolerances. Through use of the present invention anodes of extremely small dimensions may be strapped,

without the use of highly skilled workers, the completed, strapped anode having good electrical connections and excellent symmetry.

As shown in Figures 1 and 2 a symmetrical magnetron anode I0 is produced from suitable material such as oxygen free high conductivity copper and is provided with a series of resonating "cavities II with projecting vanes or segments 12 between thecavities, the structurebeing produced by bobbing or by some equivalent operation. Annular grooves I 3 are next formed at each end of the anode, preferably by turning, leaving an inner ridge M. This provides an anode body which except for machining operations incident to making of the. output circuit requires 'no further machining and is ready for strapping.

As s'hownin'Figure 3,-'the straps are fabricated from strips 20 of silver-coated or -plated copper which are machined at both ends to produce projecting portions or feet 2| and recesses 22 at ends I 23 and 24. For eflicient production the strips are stacked and a large number are produced at one time, preferably byiuse of a shaper or equivalent machine tool. The ends of the strip are next sheared off as indicated in Figure 4 to produce accurately formed straps, one of which is longer to allow for the greater circumference of the outer strap. It should be noted I that the end projections 28 are one-half the Width of the interior projections for a reason to be explained below. It should be noted that the number of complete feet in the strap is equal to half the number of segments of the anode'for the reason that each strap connects alternate segments.

In practice the straps for a magnetron of a frequency in the neighborhood of 30,000 megacycles/sec. may be of the order of five thousandths of an inch in thickness and about twelve to twenty thousandths of an inch in height. These are bent into circular shape and are intended to be spaced apart from each other and from the sides of the strapping slot by about five thousandths of an inch, in the manner shown in Figure 7.

In order to permit handling of a strap having such small dimensions and in order to maintain accuracy of assembly a jig 30 shown in Figure 5 is employed. The section in Figure 5 has been taken so as to pass at the left and right of the center through a cavity and a vane respectively. This jig is in some ways a counterpart of the anode itself, being provided with annular recesses 3| and 32 and annular projecting flanges 34, 35 and 36 which define the boundaries of the recesses. Straps 24 and 23 are bent and are placed into recesses 3i and 32 for accurate alignment and application to the anode body. Slots 3i and 32 are of such width as to provide small clearance and receive the straps snugly.

The straps shown in Figure 4 are bent and inserted into the slots as shown in Figure 5. The narrow projections 28 meet and form in effect a foot having the width and spacing of the feet 2 I. The straps are then aligned by simple visual means or by means of keys engaging the feet and permitting matching of the latter relative to projections 33. The jig is held nonrotatably against the anode by projections 33 which enter the large ends of the cavities. This results in the feet of the straps abutting against the proper alternate vanes of the anode body. By utilizing a large number of projections 33, that is, one for each cavity, centering and aligning of the straps relative to the entire anode structure is facilitated.

In actual production of strapped anodes, the machined anode of Figures 1 and 2 is held between a pair of jigs 30 made of stainless steel, each of the jigs carrying a pair of straps. The straps are previously aligned in the jigs as explained above and the jigs are clamped on each end of the anode. The entire jig and anode assembly is placed in a brazing furnace having a reducing atmosphere where a temperature above the melting point of silver but below that of the copper causes the silver coating on the straps to melt and to fuse the feet to the ends of the vanes on the anode body. Upon cooling, the

stainless steel jigs are removed from the anode without difficulty due to the fact that no bond results between the silver and the stainless steel. The finished anode is shown in Figure 6, the straps connecting alternate vanes on each end of the anode. Thus the feet of the top inner strap may abut the even numbered anode segments, while the feet of the top outer strap abut the odd numbered anode segments. In a complementary fashion, the feet of the lower inner strap would abut the odd numbered anode segments while the feet of the lower outer strap abut the even numbered anode segments.

While the method of strapping disclosed in this invention is not limited to the particular arrangement of strap connections just described, this arrangement of strap connections results in the best operation of the tube because it provides the best mode separation and greatest symmetry of the radio frequency field pattern.

It is to be noted that the connections between the feet of the straps and their respective segments take the form of a butt joint which is simple and clean to construct on a small scale.

Thus, there is provided a speedy, accurate and inexpensive method for strapping small magnetron anodes.

While I have illustrated an embodiment of my invention in conjunction with a vane and sector type of anode and have shown, by way of example, double ring strapping, it is obvious to those skilled in the art that the invention may be applied to many types of multi-segment anodes and it is not my intention to limit my invention except within the scope and extent of the appended claims.

I claim:

1. A method of strapping vane type magnetron anodes comprising forming a strap of conducting material, coating said strap with a fusible conducting outer layer, retaining said strap in a jig means, applying said jig means to the ends of the anode to obtain proper relative placement of the strap connections, fusing said fusible outer layer of said strap in order to obtain bonding between the strap and the anode, and removing the jig means after such bond has been established, said jib means being formed of material which will not bond with the fusible layer of said strap.

2. A method of manufacturing magnetron straps comprising the steps of stacking a plurality of metal sheets of which the straps are to be formed, machining parallel grooves in an edge of said stack to form spaced feet projecting therefrom and shearing from said stack a strip containing said feet to provide a plurality of identically shaped magnetron straps.

ARNOLD T. NORDSIECK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,366,164 Weick et al. Jan. 2, 1945 2,408,903 Biggs et al. Oct. 8, 1946 2,417,789 Spencer Mar. 18, 1947 2,443,445 Donal et al. June 15, 1948 2,447,537 Ronci Aug. 24, 1948 2,446,922 Wax Apr. 12, 1949 2,550,512 Woolrich Apr. 24, 1951 2,595,652 Fisk May 6, 1952 

